1. Field of the Disclosure
A method is provided which comprises storing resin cartridges in a pressurized environment. A preferred method is to store the resin cartridges in a pressurized container designed to contain singular or multiple resin cartridges, or packs of resin cartridges, and this container will double as a shipping container. The pressurized shipping and storage container slows or completely arrests the process that contributes to “limp” or depressurized resin cartridges, thus extending the shelf life of the resin cartridges. A secondary method is to store resin cartridges in a pressurized environment designed to hold multiple resin cartridges specifically to enhance the internal pressure. Thus a cartridge with lesser pressure can be modified so it now has more pressure.
2. Discussion of the Background Art
Anchor bolts are employed in various fields of engineering, for example, as strengthening or reinforcing members in rock formations and in structural bodies. The bolts are inserted into drill holes in the formation or body, and often are fixed or anchored, at their inner end or over substantially their entire length, by means of a reactive grouting composition that hardens around the bolt. When used in a mine roof, bolts grouted in this manner help significantly to prevent mine roof failure.
A reactive grouting composition can contain a resin and catalyst. Such a reactive grouting composition is typically placed in a two compartment tubular shell and is referred to as a resin cartridge. The resin cartridge should be held rigid by the internal package pressure that is created by a cartridge packaging machine when end clips are applied to the cartridge film to seal the contents.
However, within a short period of time from several weeks to several months, the cartridges become limp or lacking in stiffness or firmness. Such limp cartridges are a problem for the customer because limp cartridges are difficult to insert into overhead boreholes. It was found that one cause of the limpness was water permeating through the film and through the end clips. For example, a PET (polyethylene terephthalate) film is used throughout the industry because of its high modulus of elasticity. But a potential drawback of a PET film is a high water vapor transmission rate. Thus, any resin cartridge containing PET film as a shell, and water as a component, is subject to limpness due to loss of water volume. Reactive grouting compositions utilizing water are described in U.S. Pat. No. 4,280,943. It was also found that a second cause of limpness is expansion or creep of the PET film due to stresses created from pressurizing the contents of the resin cartridge. Creep is a permanent dimensional change in the film that comprises the shell from prolonged stress or a combination of stress and elevated temperature. The expansion or creep of the PET film reduces the internal pressure by increasing the internal volume of the resin cartridge.
Solutions that reduce water loss by covering the PET film with a barrier coating such as PVdC (Polyvinylidene chloride) or a metalized (metal impregnated) PET film work well and have been employed to reduce water loss. However, such solutions can be expensive and potentially can create problems in manufacturing resin cartridges. These solutions also do not help with the expansion of the cartridge due to PET film creep. Therefore, there is an increasing need to develop a solution that can retain the firmness or stiffness of the resin cartridge for a reasonable period time and at reasonable cost.
Resin cartridges are known to develop cosmetic defects with time. Primary among these cosmetic defects is the “limp” resin cartridge. Resin cartridges are typically manufactured with internal pressure and this internal pressure gives the package and its contents a rigidity that lends itself to easier use by the customer. A limp resin cartridge is a cartridge that has lost some or all of its internal pressure. Limp resin cartridges can be difficult to use in the mining environment. The present disclosure overcomes the disadvantages of the limp resin cartridges, by reducing the occurrence of limp resin cartridges and extending the shelf-life of the product via the novel concept of storing the resin cartridges in a pressurized environment until time of consumption. The present disclosure also describes a method to increase the internal pressure of a resin cartridge that has lost some or all of its internal pressure by storage in a pressurized environment.
The present disclosure provides many advantages, which shall become apparent as described below.